[Nexus 5 Q&A, Help & Troubleshooting] George_Mn:
Unfortunately this didn't change anything, also still on twrp. edit: internal storage also still at 0mb.

E:\Users\George_Mn\Desktop\tools>fastboot format boot
formatting 'boot' partition...
Formatting is not supported for filesystem with type 'emmc'.
FAILED ()
finished. total time: 0.101s

E:\Users\George_Mn\Desktop\tools>fastboot format cache
erasing 'cache'...
OKAY [ 0.217s]
formatting 'cache' partition...
Creating filesystem with parameters:
Size: 734003200
Block size: 4096
Blocks per group: 32768
Inodes per group: 7472
Inode size: 256
Journal blocks: 2800
Label:
Blocks: 179200
Block groups: 6
Reserved block group size: 47
Created filesystem with 11/44832 inodes and 5813/179200 blocks
sending 'cache' (13348 KB)...
writing 'cache'...
OKAY [ 1.883s]
finished. total time: 2.103s

E:\Users\George_Mn\Desktop\tools>fastboot format recovery
formatting 'recovery' partition...
Formatting is not supported for filesystem with type 'emmc'.
FAILED ()
finished. total time: 0.105s

E:\Users\George_Mn\Desktop\tools>fastboot format system
erasing 'system'...
OKAY [ 0.213s]
formatting 'system' partition...
Creating filesystem with parameters:
Size: 1073741824
Block size: 4096
Blocks per group: 32768
Inodes per group: 8192
Inode size: 256
Journal blocks: 4096
Label:
Blocks: 262144
Block groups: 8
Reserved block group size: 63
Created filesystem with 11/65536 inodes and 8536/262144 blocks
sending 'system' (18800 KB)...
writing 'system'...
OKAY [ 2.400s]
finished. total time: 2.616s

E:\Users\George_Mn\Desktop\tools>fastboot format userdata
erasing 'userdata'...
OKAY [ 0.491s]
formatting 'userdata' partition...
Creating filesystem with parameters:
Size: 13725835264
Block size: 4096
Blocks per group: 32768
Inodes per group: 8144
Inode size: 256
Journal blocks: 32768
Label:
Blocks: 3351034
Block groups: 103
Reserved block group size: 823
Created filesystem with 11/838832 inodes and 93654/3351034 blocks
sending 'userdata' (137318 KB)...
writing 'userdata'...
OKAY [ 14.469s]
finished. total time: 14.964s

sending 'bootloader' (2506 KB)...
OKAY [ 0.283s]
writing 'bootloader'...
OKAY [ 0.401s]
finished. total time: 0.688s
rebooting into bootloader...
OKAY [ 0.094s]
finished. total time: 0.096s
sending 'radio' (42033 KB)...
OKAY [ 1.467s]
writing 'radio'...
OKAY [ 2.847s]
finished. total time: 4.317s
rebooting into bootloader...
OKAY [ 0.089s]
finished. total time: 0.090s
archive does not contain 'boot.sig'
archive does not contain 'recovery.sig'
archive does not contain 'system.sig'
--------------------------------------------
Bootloader Version...: HHZ11d
Baseband Version.....: M8974A-1.0.25.0.17
Serial Number........: 032ac31c08e6b033
--------------------------------------------
checking product...
OKAY [ 0.101s]
checking version-bootloader...
OKAY [ 0.098s]
checking version-baseband...
OKAY [ 0.098s]
sending 'boot' (8620 KB)...
OKAY [ 0.488s]
writing 'boot'...
OKAY [ 0.726s]
sending 'recovery' (9202 KB)...
OKAY [ 0.541s]
writing 'recovery'...
OKAY [ 0.763s]
erasing 'system'...
OKAY [ 0.254s]
sending 'system' (692940 KB)...
OKAY [ 22.651s]
writing 'system'...
OKAY [ 44.442s]
erasing 'userdata'...
OKAY [ 0.509s]
formatting 'userdata' partition...
Creating filesystem with parameters:
Size: 13725835264
Block size: 4096
Blocks per group: 32768
Inodes per group: 8144
Inode size: 256
Journal blocks: 32768
Label:
Blocks: 3351034
Block groups: 103
Reserved block group size: 823
Created filesystem with 11/838832 inodes and 93654/3351034 blocks
sending 'userdata' (137318 KB)...
writing 'userdata'...
OKAY [ 14.418s]
erasing 'cache'...
OKAY [ 0.241s]
formatting 'cache' partition...
Creating filesystem with parameters:
Size: 734003200
Block size: 4096
Blocks per group: 32768
Inodes per group: 7472
Inode size: 256
Journal blocks: 2800
Label:
Blocks: 179200
Block groups: 6
Reserved block group size: 47
Created filesystem with 11/44832 inodes and 5813/179200 blocks
sending 'cache' (13348 KB)...
writing 'cache'...
OKAY [ 1.871s]
rebooting...

finished. total time: 87.765s
Press any key to exit...